Shock resistant circulation sub

ABSTRACT

A circulation sub and method of operating a circulation sub. The circulation sub includes a support member having a longitudinal axis and a piston movable along the longitudinal axis of the support member. A release member secures the piston to the support member. A force is applied along a length axis of the release member greater than a selected decoupling force threshold to decouple the support member from the piston, thereby allowing the piston to move along the longitudinal axis of the member.

BACKGROUND

In the resource recovery industry, a work string is lowered into a wellbore in order to perform a downhole operation, such as drilling or fluid production. The work string includes a bore therein and forms an annulus with a wall of the wellbore. At various times, such as for fracking or fluid production, it is useful to establish fluid communication between the bore and the annulus. The work string therefore includes a port between the bore and the annulus and a piston that moves axially along the work string to open and close the port. The piston is secured to the work string as the work string is being deployed downhole. Especially in horizontal wellbores, vibrators are employed on the work string in order to reduce friction between the work string and the wall of the wellbore, thereby enabling the work string to be pushed to greater depths in the wellbore without getting stuck. The force created by the vibrators can however be great enough to release the piston from the work string prematurely, allowing for possible damage to occur to the work string due to unsecured piston. Therefore there is a need to be able to better secure the piston to a work string that uses vibrators to deploy the work string downhole.

SUMMARY

In one aspect, a circulation sub is disclosed. The circulation sub includes a support member having a longitudinal axis, a piston movable along the longitudinal axis of the support member, and a release member. The release member is configured to secure the piston to the support member and to release the piston from the support member when a force applied along a length axis of the release member is greater than a decoupling force threshold of the release member.

In another aspect, a method of operating a circulation sub is disclosed. The method includes coupling a support member of the circulation sub and a piston using a release member, and applying a force along a length axis of the release member greater than a selected decoupling force threshold to decoupling the support member from the piston, thereby allowing the piston to move along the longitudinal axis of the member.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 shows an illustrative production system including a work string and circulation sub;

FIG. 2 shows a detailed illustration of the circulation sub of FIG. 1 in one embodiment;

FIG. 3 shows a close up view of a release member of FIG. 2 in one embodiment;

FIG. 4 shows a stress-strain curve for the release member; and

FIG. 5 shows a circulation sub in another illustrative embodiment.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring to FIG. 1, an illustrative production system 100 is shown. The production system 100 includes a work string 102 extending from a rig 104 located at a surface location 106. The work string 102 can be a production string or a drill string, in various embodiments. The work string 102 extends through a wellbore 108 penetrating a formation 110 and a reservoir 112 in the formation 110. A circulation sub 114 is disposed on the work string 102 at a location in the reservoir 112 for the purposes of allowing a circulation of fluid between a bore 132 of the work string and an annulus 134 between the work string 102 and a wall 108 a of the wellbore 108. In various embodiments, the circulation sub 114 can be used to perform fracking of the reservoir 112. The circulation sub 114 is disposed between a first section 102 a of the work string 102 and a second section 102 b of the work string 102. A second circulation sub 124 can be disposed at a lower end of the second section 102 b. Additional circulation subs (not shown) can also be disposed at lower sections of the work string 102. Although not shown in FIG. 1, the wellbore 108 can deviate to have a horizontal section and the work string 102 can deviate along with the wellbore 108 to extend through the horizontal section, with additional circulation subs disposed within the horizontal section.

The work string 102 includes one or more Extended Reach Tools or vibrators 130 at axially-spaced locations along the work string. The vibrators 130 reduce friction between the work string 102 and the wall 108 a of the wellbore 108, therefore allowing the work string 102 to be pushed further into the wellbore without getting stuck therein.

In various embodiments, a fluid 120 is pumped from a fluid storage device 116 through delivery pipe 118 and down through the work string 102 to exit into the reservoir 112 via the circulation sub 114. In a frac operation, the fluid can be a frac fluid and is pumped out of the circulation sub 114 and into various perforations 128 previously formed in the reservoir 112.

FIG. 2 shows a detailed illustration of the circulation sub 114 of FIG. 1 in one embodiment. The circulation sub 114 extends from a first end 240 to a second end 242. In general, the first end 240 is considered to be uphole of the second end 242 and therefore discussion of an object of the circulation sub 114 moving upward refers to the object moving towards the first end 240, while the object moving downward refers to the object moving towards the second end 242. The circulation sub 114 includes a top sub 202 at its first end 240 and a housing 204 at its second end 242. The top sub 202 is secured into the housing 204 at a threaded section 206. The top sub 202 includes a top sub axial bore 208 therethrough and the housing 204 includes a housing axial bore 210 therethrough. When the top sub 202 is secured to the housing 204, the top sub axial bore 208 is aligned with the housing axial bore 210 along a centerline or longitudinal axis 205 of the circulation sub 114, the longitudinal axis of the circulation sub being aligned with a longitudinal axis of the work string.

The top sub 202 includes an extended section 212 having a reduced outer diameter below the threaded section 206. Additionally, the housing 204 has an inner diameter below the threaded section 206 that is greater than the outer diameter of the extended section 212. The inner diameter of the housing 204 and the outer diameter of the extended section 212 therefore define a chamber 214. A leak hole or inner port 220 provides a fluid path between the top sub axial bore 208 and the chamber 214. An outer port 222 provides a fluid path between the chamber 214 and the annulus 134 of the wellbore 108.

A piston 216 resides in the chamber 214 in order to move within the chamber 214 along the longitudinal axis 205 of the circulation sub 114. The piston 216 can be secured to the top sub 202 in a first position via a release member 218. The release member 218 includes first end and a second end which are mechanically coupled by an intermediate connection. When an axial force along the length of the intermediate connection between the first end and second is greater than a decoupling force threshold of the intermediate connection, the first end becomes decoupled from the second end. In various embodiments, the release member 218 is a tensile member which includes a first end, second end and connecting shank that breaks when an axial force is applied along the length of the shank greater than a fracture threshold of the shank. In various embodiments, the release member 218 can include or refer to a plurality of circumferentially or azimuthally spaced release members. The top sub 202 serves as a support member to the piston 216 until a time at which an operator wishes to decouple the piston from the top sub 202. The piston 216 includes a flow bore therethrough arranged along the centerline of the circulation sub 144. Hence the location at which the release member 218 secures the piston 216 to the top sub 202 is radially offset from the centerline or longitudinal axis 205 of the circulation sub 144. In the first position (i.e., secured to the top sub 202), the piston 216 closes or covers both the inner port 220 and the outer port 222. Upon breaking or decoupling the release member 218, the piston 216 can move within the chamber 214. By moving downward into the housing 204 to a second position closer to the second end 242 than then first position, the piston 216 is away from the inner port 220 and the outer port 222, leaving both the inner port 220 and the outer port 222 open to chamber 214. Therefore, when the piston 216 is in the second position, fluid communication occurs between the top sub axial bore 208 and the annulus 134 via the chamber 214, inner port 220 and outer port 222.

FIG. 3 shows a close up view of the release member 218 of FIG. 2 in one embodiment. The illustrative release member 218 includes a screw or bolt having a head 302 at a first stud end and a threaded end 304 at an opposing second stud end. A length axis of the release member 218 extends from the head 302 to the threaded end 304. The length axis of the release member 218 is parallel or substantially parallel to the centerline or longitudinal axis 205 of the circulation sub 114. The head 302 secures the release member 218 to the top sub 202 while the threaded end 304 secures the release member 218 to the piston 216. A shank 306 extends from the head 302 to the threaded end 304. The shank 306 passes through a support housing 226 when the release member 218 secures the top sub 202 to the piston 216. The shank 306 include one or more support sections 308 having a first outer diameter and a stud break section 310 having a second outer diameter less than the first outer diameter. An axial force capable of breaking the stud break section 310 defines a force threshold for the release member 218.

FIG. 4 shows a stress-strain curve for the release member 218 comparing a stress (along the y-axis) to an induced strain (along the x-axis). The release member 218 stretches when an axial force is applied within an elastic range of the release member 218. The limit of the elastic range is indicated by the fracture point 402. A decoupling force threshold or fracture threshold 404 corresponds to fracture point 402 and indicates the axial force required to break the release member 218. The fracture threshold 404 is selected to be greater than a maximal force 406 applied along the length axis of the release member 218 by the vibrators 130. Therefore, the piston 216 can be secured to the top sub 202 by the release member 218 until the circulation sub 114 is deployed to its desired location in the wellbore, without the vibrators 130 breaking the release member 218.

Referring again to FIG. 2, in order to break the release member 218, a fluid pressure differential is applied between the top sub axial bore 208 and the annulus 134. An annular pressure can be in communication with the housing axial bore 210 via port 228. The piston 216 includes a flow bore and a ball seat 224 at an entry to the flow bore. A ball can be dropped onto the ball seat 224 through the top sub axial bore 208. When the ball is settled into the ball seat 224, a fluid pressure can be exerted on the ball from a surface location to create the differential pressure, for example, by using a pump at the surface location to pump a fluid through the top sub axial bore 208 to the top of the ball. At a given applied fluid pressure, the force applied to the ball, and thus on the piston 216, is greater than the fracture threshold 404 of the release member 218, thereby breaking the release member and allowing the piston to move axially within the chamber 214.

FIG. 5 shows a circulation sub 500 in another illustrative embodiment. The circulation sub 500 includes the top sub 202 and housing 204. Piston 216 is secured to the top sub 202 via a tensile ring 502 that serves as the release member. The tensile ring 502 is a generally cylindrical shell structure extending along a length axis from a first ring end 504 to a second ring end 506. The length axis of the tensile ring 502 is parallel or substantially parallel to the centerline or longitudinal axis 205 of the circulation sub 114. The first ring end 504 is secured within a first end housing 510 of the top sub 202 and the second ring end 506 is secured within the piston 216. The first ring end 504 has a flange that fits within a recess of a first end housing 510 of the top sub 202 in order to secure the tensile ring 502 to the top sub 202. The second ring end 506 has a flange that fits within a recess of the piston 216 in order to secure the tensile ring 502 to the piston 216. A ring break section 508 is located between the first ring end 504 and the second ring end 506. The ring break section 508 is designed to break when a selected force greater than a force threshold of the tensile ring 502 is applied along the length axis of the tensile ring. The ring break section 508 is designed to break before either the first ring end 504 or second ring end 506. The force threshold for the ring break section 508 can be selected by forming holes within the ring break section to weaken the ring break section by a selected amount. Alternatively, the ring break section 508 can have a thinner thickness between its inner diameter and outer diameter than either of the first ring end 504 or second ring end 506.

Although the release member is discussed as part of a circulation sub for illustrative purposes, the release member can be used in any downhole tool of the work string in various embodiments. Although the release member is discussed herein as either a tensile stud or a tensile ring, it is to be understood that any release member that breaks or decouples when a force is applied along its length axis greater than a selected decoupling force threshold can be used.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1. A circulation sub. The circulation sub includes a support member having a longitudinal axis, a piston movable along the longitudinal axis of the support member, and a release member configured to secure the piston to the support member and to release the piston from the support member when a force applied along a length axis of the release member is greater than a decoupling force threshold of the release member.

Embodiment 2. The circulation sub of any prior embodiment, wherein the decoupling force threshold of the release member is greater than the force applied along the length axis of the release member by one or more vibrators used to move the circulation sub in a wellbore.

Embodiment 3. The circulation sub of any prior embodiment, wherein the length axis of the release member is parallel to the longitudinal axis of the support member.

Embodiment 4. The circulation sub of any prior embodiment, wherein the release member is configured to break when a pressure differential between an inner bore of the circulation sub and a wellbore annulus applies the force on the release member greater than the decoupling force threshold.

Embodiment 5. The circulation sub of any prior embodiment, wherein the piston includes a ball seat for receiving a ball, wherein a fluid pressure applied to the received ball applies the force of the release member.

Embodiment 6. The circulation sub of any prior embodiment wherein the release member further comprises a tensile stud, the tensile stud having a first end securable to the support member, a second end securable to the piston and a stud break section that defines the decoupling force threshold.

Embodiment 7. The circulation sub of any prior embodiment, wherein the stud break section has a diameter smaller than a diameter of a first stud end and a diameter of a second stud end.

Embodiment 8. The circulation sub of any prior embodiment, wherein the release member further comprises a ring having a first ring end secured to the support member and a second ring end secured to the piston, the ring includes a ring break section between the first ring end and the second ring end that defines the decoupling force threshold.

Embodiment 9. The circulation sub of any prior embodiment, wherein the ring break section includes one or more holes for reducing a strength of the ring break section with respect to the strength of the first ring end and the second ring end.

Embodiment 10. The circulation sub of any prior embodiment, wherein the release member secures the piston to the support member at a location radially offset from a longitudinal axis of the circulation sub.

Embodiment 11. A method of operating a circulation sub. The method includes: coupling a support member of the circulation sub and a piston using a release member, and applying a force along a length axis of the release member greater than a selected decoupling force threshold to decoupling the support member from the piston, thereby allowing the piston to move along the longitudinal axis of the member.

Embodiment 12. The method of any prior embodiment, wherein the decoupling force threshold of the release member is greater than a force applied along the longitudinal axis of the circulation sub by one or more vibrators used to move the circulation sub in a wellbore.

Embodiment 13. The method of any prior embodiment, further comprising applying a pressure differential between an inner bore of the circulation sub and an annulus to apply the force on the release member greater than the selected decoupling force threshold.

Embodiment 14. The method of any prior embodiment, further comprising receiving a ball at the piston and applying the force along the length axis of the release member via a hydraulic pressure on the ball.

Embodiment 15. The method of any prior embodiment, wherein the release member further comprises a tensile stud, and the length axis of the tensile stud is parallel to the longitudinal axis of the support member.

Embodiment 16. The method of any prior embodiment, wherein the tensile stud includes a stud break section defining the decoupling force threshold, the stud break section having a diameter smaller than a diameter of a first stud end and a diameter of a second stud end.

Embodiment 17. The method of any prior embodiment, wherein the release member further comprises a ring having a first ring end secured to the support member and a second ring end secured to the piston, the ring includes a ring break section defining the decoupling force threshold.

Embodiment 18. The method of any prior embodiment, wherein the ring break section includes one or more holes for weakening the ring break section with respect to at least one of the first ring end and the second ring end.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity).

The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc.

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. 

What is claimed is:
 1. A circulation sub, comprising: a support member having a longitudinal axis; a piston movable along the longitudinal axis of the support member; and a release member configured to secure the piston to the support member and to release the piston from the support member when a force applied along a length axis of the release member is greater than a decoupling force threshold of the release member.
 2. The circulation sub of claim 1, wherein the decoupling force threshold of the release member is greater than the force applied along the length axis of the release member by one or more vibrators used to move the circulation sub in a wellbore.
 3. The circulation sub of claim 1, wherein the length axis of the release member is parallel to the longitudinal axis of the support member.
 4. The circulation sub of claim 1, wherein the release member is configured to break when a pressure differential between an inner bore of the circulation sub and a wellbore annulus applies the force on the release member greater than the decoupling force threshold.
 5. The circulation sub of claim 1, wherein the piston includes a ball seat for receiving a ball, wherein a fluid pressure applied to the received ball applies the force of the release member.
 6. The circulation sub of claim 1, wherein the release member further comprises a tensile stud, the tensile stud having a first end securable to the support member, a second end securable to the piston and a stud break section that defines the decoupling force threshold.
 7. The circulation sub of claim 6, wherein the stud break section has a diameter smaller than a diameter of a first stud end and a diameter of a second stud end.
 8. The circulation sub of claim 1, wherein the release member further comprises a ring having a first ring end secured to the support member and a second ring end secured to the piston, the ring includes a ring break section between the first ring end and the second ring end that defines the decoupling force threshold.
 9. The circulation sub of claim 8, wherein the ring break section includes one or more holes for reducing a strength of the ring break section with respect to the strength of the first ring end and the second ring end.
 10. The circulation sub of claim 1, wherein the release member secures the piston to the support member at a location radially offset from a longitudinal axis of the circulation sub.
 11. A method of operating a circulation sub, comprising: coupling a support member of the circulation sub and a piston using a release member; and applying a force along a length axis of the release member greater than a selected decoupling force threshold to decoupling the support member from the piston, thereby allowing the piston to move along the longitudinal axis of the member.
 12. The method of claim 11, wherein the decoupling force threshold of the release member is greater than a force applied along the longitudinal axis of the circulation sub by one or more vibrators used to move the circulation sub in a wellbore.
 13. The method of claim 11, further comprising applying a pressure differential between an inner bore of the circulation sub and an annulus to apply the force on the release member greater than the selected decoupling force threshold.
 14. The method of claim 11, further comprising receiving a ball at the piston and applying the force along the length axis of the release member via a hydraulic pressure on the ball.
 15. The method of claim 11, wherein the release member further comprises a tensile stud, and the length axis of the tensile stud is parallel to the longitudinal axis of the support member.
 16. The method of claim 15, wherein the tensile stud includes a stud break section defining the decoupling force threshold, the stud break section having a diameter smaller than a diameter of a first stud end and a diameter of a second stud end.
 17. The method of claim 11, wherein the release member further comprises a ring having a first ring end secured to the support member and a second ring end secured to the piston, the ring includes a ring break section defining the decoupling force threshold.
 18. The method of claim 17, wherein the ring break section includes one or more holes for weakening the ring break section with respect to at least one of the first ring end and the second ring end. 